DE60100224T2 - Process for the preparation of carbonic acid dialkyl esters - Google Patents

Description

1. Area of invention

The present invention relates to a method of making a dialkyl carbonate, and specifically a method of using effectively during or during the reaction a cleaning step in the production of a dialkyl carbonate, comprises reacting urea and alcohol, formed as a by-product Allophanate. The manufactured with the inventive method Dialkyl carbonate is useful as a raw material for diaryl carbonate.

2. State of the technology

The Japanese patent application No. 55-102542 describes a process for producing a dialkyl carbonate by converting urea and alcohol. The Japanese patent application Nos. 55-102543, 57-175147 and 57-26645 describe methods of Production of a dialkyl carbonate by reaction of alkyl carbamate and alcohol, and further disclose Japanese Patent Laid-Open No. 10-109960, 10-259163, 10-259166 and 11-60541 improved methods from that. In the above-mentioned prior art documents was the production of a by-product and its components however not known.

Summary the invention

The inventors found that a solid substance with an indefinite structure during manufacture of a dialkyl carbonate formed from urea and alcohol and on a condenser of a distillation column and tubes in its neighborhood is deposited. When the distillation column has been operated, without removing them, problems were caused that the pipes were blocked to flow a liquid to prevent, and an accurate flow rate was due their deposition does not appear on a speedometer. Therefore, it was necessary to use a sieve filter or the solid substance to remove in a settling vessel. Furthermore, the inventors analyzed the solid substance and found that she Allophanate is. However, the properties of allophanate were not known in detail. Therefore, allophanate was eliminated no procedure found. Because allophanate from urea or alkyl carbamate a raw material is formed as a by-product, called waste disposal of the allophanate formed as a byproduct is a lowering of the Uniform consumption of the raw material.

From the above points of view it is an aim according to the invention to provide a method for effectively using the allophanate by-product and the allophanate by-product removal apparatus and the processes to remove it.

As a result of intensive research, to allophanate as a by-product that has been eliminated so far To use effectively, the inventors found that allophanate as raw material instead of urea or together with urea can be used in the production of a dialkyl carbonate and also in a reactor to produce a dialkyl carbonate in the state an alcohol solution or a slurry returned without separation and have accomplished the present invention.

That is, the present invention provides a process for producing a dialkyl carbonate comprising reacting allophanate represented by the following general formula ( 1 ), and an alkyl alcohol represented by the following general formula ( 2 ), as raw materials, whereby a dialkyl carbonate represented by the following general formula ( 3 ), will be produced:

• (1) RO-CO-NH-CO-NH ₂
• (2) RAW
• (3) RO-CO-OR where R is an alkyl group.

In addition, the present invention provides a process for producing a dialkyl carbonate comprising reacting urea and / or an alkyl carbamate represented by the following general formula ( 4 ), and an alkyl alcohol represented by the following general formula ( 2 ), as raw materials, whereby a dialkyl carbonate represented by the following general formula ( 3 ), wherein allophanate represented by the following general formula ( 1 ), which is produced as a by-product, is used as one of the raw materials:

• (1) RO-CO-NH-CO-NH2
• (2) RAW
• (3) RO-CO-OR
• (4) RO-CO-NH ₂ where R is an alkyl group.

Short description of the drawings

1 Figure 3 is a flow diagram of the invention including continuous reaction and purification apparatus.

detailed Description of the invention

The present invention is below described in detail.

The alkyl alcohol used as a raw material for the production of a dialkyl carbonate is not limited. An alkyl alcohol with 3 to 6 Carbon atoms (R in the above general formulas: an alkyl group with 3 to 6 Carbon atoms) is preferred. Examples of alkyl alcohol include propanol, butanol, pentanol, hexanol and isomers thereof.

As another raw material can Allophanate can be used instead of urea. Although only allophanate can be used instead of urea, it is preferred allophanate obtained as a by-product to urea, alkyl carbamate or a mixture of urea and alkyl carbamate as raw materials admit.

The alkyl carbamate according to the invention is an intermediate of in the reaction of urea and the above alkyl alcohol dialkyl carbonate obtained. Although it is possible to progress the reaction letting the alkyl carbamate disappear, the reaction stopped before its disappearance, and then the alkyl carbamate from the reaction liquid recovered and can also be reused as raw material.

Any amount of urea, alkyl carbamate and allophanate is not limited. If only allophanate is used as the raw material instead of urea, the general formula ( 3 ) Dialkyl carbonate represented by reaction of the general formula ( 1 ) allophanate and one represented by the general formula ( 2 ) alcohol produced.

• (1) RO-CO-NH-CO-NH ₂
• (2) RAW
• (3) RO-CO-OR, wherein pure alkyl group and preferably an alkyl group with 3 to 6 Is carbon atoms.

Further, when allophanate is used as one of the raw materials, one represented by the general formula ( 3 ) Dialkyl carbonate represented by reaction of urea and / or by the general formula ( 4 ) alkyl carbamate represented by the general formula ( 1 ) allophanate of a by-product and one represented by the general formula ( 2 ) alkyl alcohol shown.

• (1) RO-CO-NH-CO-NH ₂
• (2) RAW
• (3) RO-CO-OR
• (4) RO-CO-NH ₂ , wherein R is an alkyl group and preferably an alkyl group with 3 to 6 Is carbon atoms.

These raw materials are mixed. In a mixture obtained in this way, the reaction is preferably carried out with heating in the presence of a catalyst. In order to allow the reaction to proceed easily, it is necessary to remove ammonia produced by the reaction from the reaction system. Therefore, it is preferable that the reactor is equipped with a reflux condenser and the reaction is carried out in the state in which the reaction liquid is heated under reflux. Alkyl carbamate is made from allophanate and urea in the early stages of the reaction. If the reaction temperature is too high at this stage, side reaction occurs. It is preferred that the reaction temperature be at the initial stage of the reaction 100 is to 200 ° C and the reaction temperature in the stage for producing a dialkyl carbonate from alkyl carbamate 160 up to 260 ° C.

It is preferred that the reaction in a high-boiling solvent with a boiling point of 180 ° C or above carried out becomes. Although it is necessary to apply pressure to the preferred one Maintain reaction temperature without a high-boiling solvent To use the reaction, use a high boiling point solvent under about atmospheric Printing done become. Examples of preferred high-boiling solvents conclude Hydrocarbons and ethers. Although the hydrocarbons aliphatic unsaturated Can be hydrocarbons are saturated Hydrocarbons or aromatic hydrocarbons with high stability prefers. Ether can aromatic ethers, aliphatic ethers or aromatic aliphatic Be ether.

Examples of preferred hydrocarbon solvents conclude Undecan, Dodecan, Tridecan, Tetradecan, Pentadecan, Hexadecan, Heptadecan, Octadecane, nonandecane, eicosane, tetramethylpentadecane, dicyclohexyl, Hexylbenzene, cyclohexylbenzene, heptylbenzene, octylbenzene, nonylbenzene, Decylbenzene, undecylbenzene, diisopropylbenzene, triisopropylbenzene, Pentamethylbenzene, methylnaphthalene, diphenylmethane, ethylbiphenyl, Bibenzyl and isomers thereof.

Examples of preferred ether solvents conclude Dihexyl ether, dioctyl ether, cyclododecyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, Triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, Butylphenyl ether, benzylphenyl ether, dibenzyl ether, diphenyl ether, Ditolyl ether and isomers thereof. It is preferred that the amount of the high-boiling solvent approximately 0.1 to 10 moles per 1 mole of the total of urea, alkyl carbamate and is allophanate as raw materials. It is preferred that the amount of alkyl alcohol approximately 0.5 to 10 moles per 1 mole of the total of urea, alkyl carbamate and is allophanate as raw materials.

As a catalyst for the reaction in the Japanese Patent Laid-Open No. 55-102542, 55-102543, 57-26645 and 57-175147 described catalyst can be used. Among them shows in particular an oxide, a hydroxide, a halide, an inorganic Salt, an organic salt, an alkoxide, an alkyl substituted one Oxide or an alkyl alkoxide selected from at least one metal the group consisting of zinc, lead, copper, tin, titanium, gallium and indium high activity for the Reaction.

The reaction can be carried out in a batch process or in a continuous process. In a batch process it is before entails that the total amount of alkyl alcohol is not added at the start of the reaction, but is gradually added as the reaction proceeds. In a continuous process, it is preferred that the reaction be carried out in a cascade process with multiple reactors. It is preferred that the number of reactors 3 to 5 is. Alkyl alcohol can be fed to any reactor.

After the reaction has ended the intended dialkyl carbonate by means of separation by distillation from the reaction liquid be preserved. It is possible, both the catalyst and that in the reaction liquid contained high-boiling solvents as a high-boiling matter in distillation and alkyl alcohol to separate as low-boiling matter in the distillation. allophanate is separated together with alkyl alcohol as a low-boiling material, because it is a sublimation substance.

Despite the liquid removed can both low-boiling matter and high-boiling matter as Dialkyl carbonate can be used, if necessary further distillation cleaning carried out become. In this case it is possible as described in Japanese Patent Laid-Open No. 2000-1461 promote separation by adding a third substance.

Allophanate contained in the alkyl alcohol can be separated by filtration as it is separated by cooling becomes. In order to carry out the separation efficiently, it is preferred that a settling vessel be installed is and then deposited allophanate in its bottom area is filtered off. Allophanate thus separated is not only considered as Raw material but also together with urea and / or alkyl carbamate used as one of the raw materials.

It is industrially preferred that an alkyl alcohol solution of allophanate obtained by distillation or a slurry thereof than the raw material for the reaction is used because the efficiency is low if Allophanat is filtered off. The total amount of distilled water separated alcohol can be returned to the reactor because of the alkyl alcohol is not implemented, and its total amount is less than that for the reaction needed Amount is. Therefore, the reaction can be done by adding urea and / or Alkyl carbamate and alkyl alcohol are carried out to the liquid again.

Preferred embodiment the invention

The present invention is below in more detail with reference to examples that are not intended to do so are to limit the scope of the present invention.

The one described in the examples Word "butyl" means "n-butyl".

example 1

One with a detachable piston a capacity 500 ml reactor connected to a baffle with an Allihn cooler and a stirrer with shovel blades attached was used. hot Water at 60 ° C was through the cooler guided. 25.00 g (156 mmol) butyl allophanate, 5.70 g (76.9 mmol) butanol, 2.89 g (11.6 mmol) of dibutyltin oxide and 214.70 g (1.26 mol) of diphenyl ether were filled into the reactor and 4 hours with stirring while Heat in an oil bath implemented. It was assumed that the time when the temperature the reaction liquid Reached 130 ° C, the reaction start time was. Then the temperature was adjusted around 180 ° C after 1 hour of reaction start, 200 ° C after 2 hours and 205 to 210 ° C after 4 To hold for hours. The oil bath temperature was gradually of 160 ° C at the time of starting the reaction at 235 ° C at the time of finishing the reaction elevated. Butanol was during added to the reaction so as not to excessively raise the reaction temperature. The The total amount of butanol used as the raw material was 33.37 g (450 mmol). After the completion of the reaction, the yield of dibutyl carbonate was 36.24 g (208 mmol). The yield of dibutyl carbonate based on Butyl allophanate was 66.7%.

Example 2

The response was the same Way as performed in example 1 except that 12.50 g (78.0 mmol) of butyl allophanate and 9.37 g (156 mmol) of urea instead of 25.00 g of butyl allophanate were used as raw material, and the addition of butanol was changed from 5.70 g to 17.38 g (234.5 mmol). The The total amount of butanol used as the raw material was 38.54 g (520 mmol). After the reaction was completed, the yield of dibutyl carbonate was 33.80 g (194 mmol), and the yield of dibutyl carbonate based on the total amount of butyl allophanate and urea was 62.2%.

Example 3

The reaction and purification were as in 1 shown using four stage continuous reactors and three distillation columns. In each of the reactors 1 . 2 . 3 and 4 a 350 liter capacity vessel equipped with a baffle and a stirrer was used. 0.037 mol of dibutyltin oxide and 4 mol of diphenyl ether per 1 mol of urea were added to the premixing vessel 15 added to be uniformly dispersed, and then continuously through the discharge pipe 9 introduced into the reactor. The insertion speed was adjusted to obtain 100 kg / h. Heating was done by passing a heated medium of 230 ° C through a coil in carried out each reactor. The temperature in each reactor was adjusted to 170 ° C in reactor 1 , 180 ° C in the reactor 2 , 190 ° C in the reactor 3 and 200 ° C in the reactor 4 to keep. Butanol was over the drain pipe 10 introduced to maintain the reaction temperature at a prescribed temperature. The amount of through this drain pipe 10 supplied butanol during steady-state operation was 10 kg / h. Hot water of 60 ° C was passed through the reflux condensers 5 . 6 . 7 and 8th carried out. The reaction liquid was drained through the reaction liquid withdrawal pipes 11 . 12 . 13 and 14 connected to each reactor to keep the amount of liquid in each reactor at 230 liters. Ammonia was formed from each reactor of butanol through reflux condensers 5 . 6 . 7 and 8th separated and then over the drain pipe 16 dissipated.

The reaction liquid was fed into the distillation column through the discharge pipe 14 filled. The insertion speed was 108 kg / h. The distillation column 17 was adjusted to maintain a column head pressure of 2.7 kPa, a column head temperature of 102 ° C and a column bottom temperature of 145 ° C. The column bottom liquid, which was a mixture of the catalyst and diphenyl ether, was added to the premix vessel 15 via the drain pipe 20 returned for reuse.

The mixture of butanol, dibutyl carbonate, butyl carbamate, diphenyl ether and butyl allophanate obtained from the upper part of the column was fed into the distillation column 18 via the drain pipe 21 introduced. The distillation column 18 was adjusted to maintain a column head pressure of 13.3 kPa, a column head temperature of 67 ° C, and a column bottom temperature of 140 ° C. Butanol and butylallophanate were obtained from the column top area and into the reactor 1 via the drain pipe 22 supplied as a slurry liquid of butyl allophanate. The feed amount was butanol 3 kg / h and butyl allophanate 150 g / h.

The mixture of dibutyl carbonate, butyl carbamate and diphenyl ether was added to the distillation column 19 via the drain pipe 23 introduced. To ensure sufficient separation of dibutyl carbonate and butyl carbamate, phenol was passed through the drain pipe 24 into the distillation column 19 introduced. The distillation column 19 was adjusted to maintain a column head pressure of 2.7 kPa, a column head temperature of 91 ° C and a column bottom temperature of 125 ° C. A mixture of dibutyl carbonate and phenol was removed from the column top area via the drain pipe 26 receive. A mixture of butyl carbamate and diphenyl ether obtained from the column bottom area was put in the premixing vessel 15 via the drain pipe 25 returned for reuse.

After introducing butyl carbamate into the premixing vessel 15 via the drain pipe 25 had started, the feed amount of urea was adjusted to hold 1 mol of the final total of butyl carbamate and urea per 4 mol of diphenyl ether.

The apparatus was operated continuously for 80 hours. The steady state was reached 30 hours after the start of operation. The rate of supply of urea in the steady state was 72.5 mol / h, whereas the rate of production of dibutyl carbonate was that of the reaction liquid withdrawal tube 14 was obtained was 72.2 mol / h (99.6 mols on urea fed). The urea-based yield of dibutyl carbonate was 2.6 more than in Comparative Example 1, in which butyl allophanate was not to the reactor 1 was returned.

Comparative Example 1

The operation was 80 hours in the same apparatus and with the same procedure as in the example 1 except that butyl allophanate was cooled to 5 ° C to be installed in a settling vessel in a lower part of the condenser of the distillation column 18 to separate and only butanol through the drain pipe 22 in the reactor 1 was returned. But to remove butyl allophanate, procedures were necessary to remove butyl allophanate from the settling vessel every hour and filtering it off from butanol. The rate of supply of urea in a steady state was 73.3 mol / h, whereas the rate of production of dibutyl carbonate was via the reaction liquid withdrawal tube 14 was obtained, was 71.1 mol / h (97.0 mol% on urea fed).

The present invention provides a new process for the production of dialkyl carbonate. Further is according to the inventive method the unit consumption of raw material increases, and a step of separation removal Allophanate can be used in a process for the production of dialkyl carbonate be eliminated.

Claims (11)

A process for producing a dialkyl carbonate comprising reacting allophanate represented by the following general formula ( 1 ), and an alkyl alcohol represented by the following general formula ( 2 ), as raw materials, wherein a dialkyl carbonate represented by the following general formula ( 3 ), is produced: (1) RO-CO-NH-CO-NH ₂ (2) ROH (3) RO-CO-OR where R is an alkyl group. The method of claim 1, wherein R is an alkyl group having 3 to 6 carbon atoms. The method of claim 1 or 2, wherein the Reaction is carried out in the presence of a catalyst. The method of claim 3, wherein the catalyst an oxide, a hydroxide, a halide, an inorganic salt organic acid salt, an alkoxide, an alkyl substituted oxide or an alkyl alkoxide at least one metal from the group consisting of zinc, lead, copper, tin, titanium, gallium and indium, is. Method according to one of claims 1 to 4, wherein the reaction is carried out at a temperature of 100 to 260 ° C. Method according to one of claims 1 to 5, wherein the reaction in a high-boiling solvent with a boiling point of 180 ° C or higher carried out becomes. A process for producing a dialkyl carbonate comprising reacting a urea and / or an alkyl carbamate represented by the following general formula ( 4 ), and an alkyl alcohol represented by the following general formula ( 2 ), as raw materials, wherein a dialkyl carbonate represented by the following general formula ( 3 ), wherein allophanate represented by the following general formula ( 1 ), which is produced as a by-product, is used as one of the raw materials: (1) RO-CO-NH-CO-NH ₂ (2) ROH (3) RO-CO-OR (4) RO-CO-NH ₂ where R is an alkyl group. The method of claim 7, wherein R is an alkyl group with, 3 to 6 carbon atoms. The method of claim 7 or 8, wherein the allophanate is separated by filtration. A method according to any one of claims 7 to 9, wherein the allophanate separated and then together with urea as raw material is fed into a reactor. A method according to any one of claims 7 to 10, wherein the allophanate as a slurry or as a solution of alkyl alcohol represented by the general formula ( 2 ) is fed into a reactor without performing the separation.